Server Issue- Clockwork HL2RP server lagging at 15 to 20 players

Recently, my server has been experiencing lag when the server is holding 15 to 20 players, however for players, pings for the players do go up as well. There is nobody attacking the server, as the TeamSpeak server and Murder server are not lagging at all, and the lag is experienced in the HL2RP server. We have over 100+ props on the map that are static, and it’s not determined that is the source of the lag. We have not had this issue before with lag, with these props, however now that there is a good 20 players on everyday, the lag is becoming more prevalent, and people are having issues RPing which have lead to auto-disconnects.

Would increasing the RAM make a change in the way the server handles the player-load? Or would the box be an issue in general.

Out of our total network utilization, we use .36% of total network usage. Our RAM usage is 4 and a half gigabytes out of 32 gigabytes.

-tickrate 33
or
-tickrate 15

Do -tickrate 33. Anything under that causes major prediction errors.